Fluorescein, Rose Bengal, Indocyanine Green

Mechanism

💊 Commercial Names

Colircusi Fluorescein, BioGlo Strips, Water-soluble Indocyanine Green, Rose Bengal Strips.

🔬 Pharmacological Group

Diagnostic fluorophore organic dyes. Selective staining and contrast agents.

Mechanism of Action

Each dye has optical properties and tissue affinities that define its usefulness in ophthalmic consultation:

• Sodium Fluorescein: Water-soluble fluorophore that absorbs light in the blue wavelength band (465-490 nm) and intensely emits yellowish-green fluorescent light (520-530 nm):
  1. Corneal Epithelial Defect Staining: In an intact and healthy corneal epithelium, tight junctions prevent the diffusion of fluorescein. In the event of an erosion, ulcer or mechanical defect, the dye diffuses freely through the intercellular spaces of the adjacent hydrophilic corneal stroma, staining the defect bright green under cobalt light.
  2. Fluorescein Angiography (FVA): Injected via peripheral intravenous route, it precisely delimits the retinal blood vessels, revealing areas of capillary ischemia or pathological leakage due to breakdown of the internal blood-retinal barrier.
• Rose Bengal and Lysamine Green: They specifically stain devitalized, dead or degenerated corneal and conjunctival epithelial cells, as well as areas where the tear film has locally lost its protective layer of dural mucin. They are of great value in evaluating conjunctival severity in primary Sjögren's Syndrome. Rose bengal also has weak cellular epitheliotoxicity.
• Indocyanine Green (ICG): Near-infrared fluorophore that has a high percentage of binding to plasma proteins (98%), being strictly confined in the choroidal vascular lumen. It allows high-resolution angiographic visualization of deep choroidal microcirculation through retinal pigmentation and RPE hyperplasia.

Pharmacokinetics

Quantitative Ocular and Systemic Pharmacokinetics

Security

Risk of Anaphylactic Shock in Fluorescein Angiography

Systemic intravenous injection of 10% fluorescein sodium or indocyanine green may trigger dose-independent severe idiopathic anaphylactoid reactions. In susceptible patients, massive non-IgE systemic degranulation of mast cells and basophils occurs with the release of histamine, inducing anaphylactic shock, severe bronchospasm, laryngeal edema, and cardiorespiratory arrest with a fulminant course. The procedure requires the prior signing of the informed consent and the immediate availability of a cardiopulmonary arrest cart with adrenaline, injectable corticosteroids and oxygen support for rapid use.

Contraindications

• Absolute (For diagnostic IV injection): Personal history of previous allergic reaction or anaphylaxis to fluorescein sodium or indocyanine green; known hypersensitivity to iodine (in the case of indocyanine green, since the commercial salt contains a minor percentage of iodine and can induce cross-anaphylaxis).
• Relative (Topical Use): Extensive epithelial keratitis in patients who permanently wear hydrogel contact lenses (permanently stains the lens yellowish-green).

Adverse Effects (ADR)

• Ocular Locals (Topical): Stinging and transient irritation of the conjunctival surface; reflex tearing; temporal eyelid and tear staining of yellow-green color.
• Systemic (Intravenous AVF): Sudden nausea and repeated self-limited vomiting during injection (very common, occurs in 5-10% due to transient direct vagal stimulation); skin itching and generalized urticaria; yellowish staining of the skin and urine for 24-36 hours; very rare acute myocardial infarction induced by the dural stress of the procedure.